When my Dad was on Shacks in Malta (1956) they had ASV13.
He says they largely relied on visual detection of Submarines and only used ASV13 at night when but they still relied on Flares and visuals.
I think in those days the Med was pretty clean and clear around Malta.
He has told me that had an MR2 with an Airborne Lifeboat fitted (and Lindholme gear) when he arrived. They only had one lifeboat (I kid you not) and were told it was not to be used except in an emergency. Shortly afterwards it was withdrawn from use and they were given authorisation to drop the Lifeboat. Guess what - it sank without trace.......................
He had a great time on Shacks for 2 years before being posted back to UK.
Arc